JP6113953B2 - Filter materials and filter composites - Google Patents

Description

  The present invention relates to a filter material and a filter composite material having a function of collecting and removing contaminants in the air, such as dust, and cleaning the air.

  Meta-aramid fiber, fluorine-based fiber, polyphenylene with excellent heat resistance and chemical resistance are used as the fiber constituting the filter material for filtering high-temperature exhaust gas discharged from garbage incinerators, coal boilers, metal blast furnaces, etc. A filter material made of a nonwoven fabric using sulfide fiber, polyimide fiber, or the like has been used. Among these, meta-aramid fibers are widely used as a dust collection bag filter for coal boilers because they have excellent hydrolysis resistance, acid resistance and alkali resistance.

However, at present, environmental regulations tend to be stricter, and there is a demand for a bag filter with higher dust collection efficiency than the bag filter using the heat-resistant fiber. This is a bag filter used in, for example, a gasification and melting treatment furnace, and there is a demand for a filter that can collect dust having a small particle diameter and that is superior in dimensional stability at higher temperatures .

  In view of this, a method has been proposed in which a microporous film of a fluororesin is bonded to the felt surface of a heat resistant fiber, and dust is collected with high efficiency by the microporous film (Patent Document 1). Certainly, this method has a high efficiency of collecting fine dust of 0.5 μm or less, but has a problem that it peels off due to poor adhesion between the microporous film of fluororesin and multiple materials.

  Alternatively, the ultrafine fiber layer and the felt base layer are integrated by needle punching, the distribution of the ultrafine fiber is gradually reduced from the front surface to the back surface, and then the ultrafine fiber is divided by a high-pressure water flow punch. There is a filter with high collection efficiency that makes it extremely fine (Patent Document 2). However, in this filter, it is necessary to laminate two or more kinds of different fibers, and there is a problem that there are many processing steps.

  In addition, a filter cloth for a highly filterable bag filter mixed with at least one of PPS fibers and polyimide, polyamideimide, polytetrafluoroethylene, and glass fibers has been proposed (Patent Document 3). However, this invention uses a PPS fiber having a dry heat shrinkage of 180 ° C. of 3% or more, and does not improve the dimensional stability of a nonwoven fabric filter using the PPS fiber. Moreover, when mixing a PPS fiber and another fiber, there exists a problem that a mixing nonuniformity tends to generate | occur | produce.

In addition, a filter cloth in which fluorine fibers are entangled on the surface of a base material having heat resistance has been proposed ( Patent Document 4 ). This method is surely good in terms of dust peeling performance and prevention of particle penetration into the filter cloth and suppressing pressure loss during operation of the dust collector. However, there are problems that the air permeability in the initial state is low and the initial pressure loss is high, leading to a shortened life of the filter cloth and a significant reduction in exhaust gas treatment capacity. Furthermore, there is a problem that a plurality of processing steps are required in which a web made of staple fibers of polytetrafluoroethylene is laminated and entangled after the felt of the base material having heat resistance is produced. And there exists a problem which the web layer which consists of the laminated fiber of a polytetrafluoroethylene peels by the impact in use as a bag filter.

JP 2000-140588 A JP-A-5-192520 JP 2000-140530 A JP 2002-204909 A

  The present invention has been made in the background of the above-mentioned prior art, and its purpose is excellent in heat resistance and flame retardancy, hardly shrinks even in a high temperature atmosphere, and collection efficiency of fine dust having a particle size of submicron order. The object is to provide a filter material with an improved resistance.

As a result of intensive investigations, the present inventors have constituted continuous fibers having a specific fiber diameter, melting point or thermal decomposition temperature, and satisfied the apparent density , average pore diameter, and dry heat shrinkage as the characteristics of the nonwoven fabric. When the nonwoven fabric to be used is used, it discovered that the filter material which can solve the said subject was obtained, and came to complete this invention.

Thus, according to the present invention, the nonwoven fabric is composed of continuous fibers, the continuous fibers satisfy (a) and (b), and the nonwoven fabric satisfies (c), (d), and (e). A filter material is provided.
(A) The average fiber diameter of continuous fibers on the nonwoven fabric surface is 0.1 to 10 μm.
(B) Melting point or thermal decomposition temperature of continuous fiber is 300 ° C. or higher (c) Apparent density of nonwoven fabric is 0.05 to 1.0 g / cm ³
(D) The average void diameter of the nonwoven fabric is 0.5 to 10 μm, and the maximum void diameter is 20 μm or less. (E) The dry heat shrinkage rate at 200 ° C. of the nonwoven fabric is 2% or less. There is provided a filter composite material characterized by being laminated with a fiber structure made of any one of a woven fabric, a knitted fabric, a non-woven fabric, or a combination thereof.
Furthermore, the bag filter characterized by the said filter material or the said filter composite material being sewed in the shape of a bag is provided.

  The filter material, filter composite material, and bag filter of the present invention are composed of a nonwoven fabric composed of continuous fibers having a small average fiber diameter, and the nonwoven fabric has appropriate voids, so that fine particles can be collected. It is. In addition, since the thermal dimensional stability is excellent and the shrinkage due to heat is small, even when used in a high temperature atmosphere for a long period of time, it is possible to maintain excellent dust removal properties.

The present invention is illustrated by the following preferred examples, but is not limited thereto.
The filter material of the present invention comprises a nonwoven fabric composed of continuous fibers, the continuous fibers satisfy (a) and (b) described later, and the nonwoven fabrics (c), (d) and (e) described later. As a result, it has a dense structure with a low degree of freedom of movement of fibers and is difficult to shrink, and can be used in high-temperature atmospheres such as incinerators, coal boilers, or metal blast furnaces. The filter material has excellent heat resistance and excellent dimensional stability even in a high temperature range. Hereinafter, the requirements (a) to (e) will be described in detail.

(A) The average fiber diameter of continuous fibers on the nonwoven fabric surface is 0.1 to 10 μm. When the average fiber diameter is larger than 10 μm, the number of fiber components in the nonwoven fabric is reduced, and the density of the nonwoven fabric is reduced. In addition, the space contained in the nonwoven fabric is increased, and fine dust cannot be collected. A filter with low collection efficiency. On the other hand, when the average fiber diameter is smaller than 0.1 μm, the obtained strength is remarkably lowered, and the fiber is easily damaged by a physical impact given when dust is removed. More preferably, an average fiber diameter is 0.3-8 micrometers, More preferably, it is 0.5-5 micrometers.
In addition, the average fiber diameter of the continuous fibers constituting the nonwoven fabric of the present invention means the diameter of the fiber that can be confirmed by an electron micrograph of the nonwoven fabric surface, and arbitrarily select 100 fibers and measure the width. The average fiber diameter can be determined by averaging.

The basis weight and thickness of the nonwoven fabric used as the filter material of the present invention are not particularly limited, but the basis weight is 5 g / m ² or more and the thickness is 10 μm or more from the viewpoint of filter collection performance. preferable. If the basis weight is smaller than 5 g / m ² and the thickness is smaller than 10 μm, the space contained in the nonwoven fabric is small, and a desired average apparent density and average void diameter described later tend to be difficult to obtain.

(B) The melting point or thermal decomposition temperature of the continuous fiber is preferably 300 ° C. or higher. This is because the exhaust gas discharged from a garbage incinerator, coal boiler, metal blast furnace or the like has a high temperature of 150 to 200 ° C., and the filter material used is required to have high heat resistance. If the continuous fiber melting point or thermal decomposition temperature is 300 ° C or higher, it should be a useful filter material with very little generation of foreign matters such as fiber scraps and melt-degraded materials even in harsh usage environments that receive high friction at high temperatures. Can do. Moreover, a filter material can also be comprised only with a single nonwoven fabric, and even in that case, stable filter performance is exhibited as a uniform nonwoven fabric without uneven distribution with other components. The melting point or thermal decomposition temperature of the continuous fiber is more preferably 350 ° C. or higher, and further preferably 400 ° C. or higher.
The “melting point or thermal decomposition temperature” in the present invention can be determined from a differential thermal analysis curve obtained by differential thermal analysis according to JIS K7121.

(C) The apparent density of the nonwoven fabric is 0.04 to 1.0 g / cm ³ . If the apparent density of the nonwoven fabric is less than 0.04 g / cm ³ , dust collection efficiency is lowered, which is not preferable. Further, when external pressure is applied, the thickness tends to decrease, and the handleability is poor. On the other hand, if the apparent density of the nonwoven fabric exceeds 1.0 g / cm ³ , the pressure loss increases, so that clogging is accelerated and the life performance of the filter is shortened, which is not preferable. Moreover, in order to obtain a desired thickness, it is necessary to increase the fiber accumulation amount, which is uneconomical. The apparent density of the nonwoven fabric is preferably 0.075 to 0.75 g / cm ³ , more preferably 0.1 to 0.5 g / cm ³ .

  (D) The nonwoven fabric has an average pore size of 0.5 to 10 μm and a maximum pore size of 20 μm or less. When the average void diameter is larger than 10 μm or the maximum void diameter is larger than 20 μm, the performance of collecting fine dust is inferior. On the other hand, when the average void diameter is less than 0.5 μm, the pressure loss increases. It is not preferable because clogging is fast and the life performance of the filter is shortened. The average void diameter of the nonwoven fabric is preferably 0.75 to 7.5 μm, more preferably 1 to 5 μm, and the maximum void diameter of the nonwoven fabric is preferably 15 μm, more preferably 10 μm.

  (E) The dry heat shrinkage of the nonwoven fabric at 200 ° C. is 2% or less. When the dry heat shrinkage rate is larger than 2%, the collected dust is restrained by the shrinkage of the filter material in an environment used at a high temperature, the wiping property is lowered, and the pressure loss is increased. For this reason, clogging is quick and the life performance of the filter is shortened, which is not preferable. The dry heat shrinkage rate at 200 ° C. of the nonwoven fabric is preferably 1.75% or less, more preferably 1.5% or less.

The present invention has been found that, by satisfying the above (a) to (e) at the same time, these effects are combined to exhibit excellent filter performance even in a high temperature atmosphere.
The continuous fibers constituting the non-woven fabric are carbon fibers, glass fibers, ceramic fibers, asbestos fibers and other inorganic fibers, aramid fibers, vinylon fibers, polyarylate fibers, polyparaphenylene benzobisoxazole (PBO) fibers, polyphenylene sulfide fibers, Examples thereof include organic fibers such as wholly aromatic polyester fibers, acrylic fibers, vinyl chloride fibers, polyketone fibers, cellulose fibers, and pulp fibers. These can be used alone or in combination of two or more. Among them, aramid fibers such as poly-metaphenylene isophthalamide fiber, which is a meta-type aramid fiber, and polyparaphenylene terephthalamide, which is a para-type aramid fiber, and copolyparaphenylene 3,4'oxydiphenylene terephthalamide, have high strength, Heat resistance and filter performance can be satisfied at the same time, which is preferable.

  About the manufacturing method of the nonwoven fabric used for the filter material of this invention, when using organic fiber, for example, it can obtain by spinning of the polymer solution. Preferable specific examples include explosive spinning technology (described in WO02 / 052070) for bursting an organic polymer solution to make it fine, and the electrospinning method disclosed in Japanese Patent Application Laid-Open No. 2005-200779.

  In the present invention, the nonwoven fabric used for the filter material is made of continuous fibers obtained by discharging a polymer solution from a discharge hole, blowing an air flow on the solution, and continuously solidifying the discharged polymer without bursting. It is preferable that it is a nonwoven fabric.

  Specifically, as a method for producing the nonwoven fabric, a polymer solution is ejected using a technique (US Pat. No. 6,013,223) that improves the melt-blowing technique performed with a thermoplastic polymer and effectively fines the fiber. The polymer solution can be stretched and thinned by discharging the compressed air from the compressed air discharge hole installed on the concentric circle of the polymer discharge hole of the spinning device. At this time, the fiber diameter of the constituent fibers can be adjusted by changing the hole diameter of some of the polymer discharge holes or changing the amount of compressed air blown out from some of the pressure discharge holes. In addition, the ratio of the number of constituent fibers having different fiber diameters can be arbitrarily adjusted by changing the hole diameter as described above or the number of polymer discharge holes changing the amount of compressed air. In the above method, continuous fibers with a uniform and uniform fiber diameter can be formed without burring and cutting the discharged polymer as in the explosive spinning technique, and a nonwoven fabric can be obtained. Further, the discharged polymer can be solidified by contacting with a gas such as air or contacting with a coagulating liquid. Examples of the coagulating liquid include water, a mixed liquid of water and an amide polar solvent, a mixed liquid of water and alcohols, and alcohols.

  In the present invention, when an aramid continuous fiber is used as the continuous fiber, the crystallinity obtained from X-ray diffraction of the continuous fiber is preferably 55% or less or the crystal size is 30 mm or less from the viewpoint of filter performance. . Such crystallinity and crystal size can be obtained by discharging the above polymer solution from the discharge hole and blowing an air stream to the polymer to continuously solidify the discharged polymer without bursting. Can be achieved.

In this way, the filter material of the present invention can be produced, but there may be a variation in thickness or the tensile strength may not be within a desired range. In such a case, when the continuous fiber constituting the nonwoven fabric is an organic fiber, the above-mentioned problem is caused by performing a calendar process (calendar process) at a temperature lower than the softening temperature (preferably a temperature lower by 20 ° C. or more). Is preferably solved. The pressure in the calendar process is not particularly limited because it varies depending on the degree of thickness variation, desired apparent density , desired tensile strength, desired tear strength, and the like. This pressure can be appropriately set by repeating the experiment.

  The nonwoven fabric used as the filter material of the present invention can be used in a single-layer structure made of a single material, but it has a multilayer structure composed of two or more materials for the purpose of further improving the handleability and increasing the thickness. There may be. In that case, it can be set as the filter composite material formed by laminating | stacking the nonwoven fabric used as a filter material, and one or more fiber structures. The fiber structure may be a woven fabric, a knitted fabric, a non-woven fabric, or a combination thereof.

Although the diameter of the fiber which comprises the said fiber structure is not specifically limited, From a viewpoint of intensity | strength or thickness, it is preferable that it is 5 micrometers or more.
Moreover, although the fabric weight of the said fiber structure is not specifically limited, 40-2000 g / m < ² > is preferable. If it is less than 40 g / m ² , the rigidity is low and the handleability is poor, and if it exceeds 2000 g / m ² , the weight cannot be reduced, the flexibility is lowered, and the cost is increased. More preferably, it is 50-1500 g / m < ² >, More preferably, it is 60-1300 g / m < ² >.

The fiber constituting the fiber structure is not particularly limited, but is inorganic fiber such as carbon fiber, glass fiber, ceramic fiber, asbestos fiber, aramid fiber, vinylon fiber, polypropylene fiber, polyethylene fiber, polyarylate fiber Organic fibers such as polyparaphenylene benzobisoxazole (PBO) fiber, polyphenylene sulfide fiber, nylon fiber, polyester fiber, wholly aromatic polyester fiber, acrylic fiber, vinyl chloride fiber, polyketone fiber, cellulose fiber, pulp fiber, etc. These can be used alone or in combination of two or more. Among them, poly-metaphenylene isophthalamide fiber, which is a meta-type aramid fiber, poly-paraphenylene terephthalamide, which is a para-type aramid fiber, and copolyparaphenylene 3,4'oxydiphenylene terephthalamide, have high strength and high heat resistance. This is preferable.

  As a method for producing the filter composite material of the present invention, the above filter material and the fiber structure can be laminated, and then subjected to heat treatment, pressure heat treatment, or the like to firmly bond them. In addition, when laminating the filter material and the fiber structure, an adhesive is applied to either or both of the filter material and the fiber structure on the surface where the filter material and the fiber structure are bonded, and these are bonded more firmly. You may let them. By performing such an adhesion process, the adhesion between the filter material and the fiber structure is improved, and a filter composite material with more excellent workability and handleability can be obtained.

The adhesive is not particularly limited, but an organic adhesive such as an acrylic resin adhesive, a urethane resin adhesive, an epoxy resin emulsion adhesive, a vinyl acetate resin emulsion adhesive, or a silicone adhesive. And inorganic adhesives such as silica-based adhesives.

  The heat treatment method is not particularly limited, and examples thereof include heat treatment such as through-air processing, pressure heat treatment such as calendar processing and embossing. In the pressurization heat treatment, a processing temperature of 30 to 350 ° C. and a linear pressure of 30 to 300 kg / cm can be preferably employed.

  The filter composite material may be a laminate of a filter material and a fiber structure. Furthermore, it is good also as a structure which provided the fiber structure layer further on the filter material laminated | stacked on the fiber structure, and pinched | interposed the filter material with the fiber structure.

The filter material and filter composite material obtained as described above are suitably used as a bag filter that is sewn into a bag shape and collects exhaust gas from a dust incinerator, a coal boiler, or a metal blast furnace that requires heat resistance. As a sewing thread used for sewing, it is preferable to use a thread made of a fiber material having chemical resistance and heat resistance, like a fiber constituting a woven fabric, such as a meta-aramid fiber or a fluorine-based fiber. Used as appropriate.
Further, the filter material and the filter composite material are suitable for a filter material for a cartridge filter or a liquid filter because they are flexible and excellent in winding processability.

  The present invention will be specifically described below with reference to examples. However, the present invention is not limited thereby. The evaluation and characteristic values of the following examples and the like were determined by the following measurement methods.

(1) Fiber diameter (μm)
The nonwoven fabric is observed with a scanning electron microscope JSM6330F (manufactured by JEOL), 100 fibers are arbitrarily selected and measured, and a fiber (A) having a fiber diameter of 0.1 to 5 μm and a fiber diameter of 5 to 5 are used. The ratio of the fiber which comprises a nonwoven fabric was computed from the fiber number of the fiber (B) which is 100 micrometers. The observation was performed at 1000 times.

(2) Weight per unit (g / m ² )
The basis weight was measured based on the following test method of weight per unit area.
Three test pieces of the same size of 500 cm ² or more are collected from the sample per 1 m of the sample.
Measure the weight of the test piece in the standard state.
The weight per unit area is calculated by the following formula and rounded to 3 significant figures according to JIS Z 8401.

(3) Thickness (mm)
Ono Sokki Using a digital linear gauge DG-925 (diameter of the measurement terminal part 1 cm), the thickness was measured at 20 arbitrarily selected locations, and the average value was obtained.

(4) Apparent density (g / cm ³ )
The weight per unit volume was calculated from (weight per unit area) / (thickness).

(5) Average void diameter (μm), maximum void diameter (μm)
The average void diameter and the maximum void diameter were determined by the bubble point method and the mean flow method described in ASTM- F-316.

(6) Melting point, thermal decomposition temperature (° C)
According to JIS K7121, the melting point and the thermal decomposition temperature were determined from a differential thermal analysis curve obtained by differential thermal analysis.

恒温乾燥機を用い、この装置中に試験片をたて方向に鉛直になるように隅をつかんでつりさげ、無緊張状態として、装置の指示目盛が２００℃となった後、１５分間器内に放置し、取り出して室温まで冷却する。
初めに印をつけた、たて、よこ方向のそれぞれ３か所の長さを０．１ｍｍまで測定する。
次の式によって収縮率を算定し、さらに、たて及びよこのそれぞれについてその平均値を求め、ＪＩＳ Ｚ ８４０１ によって小数点以下１けたに丸める。

(7) Dry heat shrinkage (%)
By the following method , the dry heat shrinkage rate of the nonwoven fabric after heat treatment at 200 ° C. for 15 minutes was determined in an unstrained state.
Three test pieces of about 25 cm × 25 cm are collected from the sample per 1 m of the sample.
As shown in the figure below, the test piece is marked with a mark indicating exactly 20 cm in length at each of three sides.

Using a constant temperature dryer, hold the corner so that the test piece is vertically vertical in this device and hang it, and as an untensioned state, the indication scale of the device reaches 200 ° C. Leave it to cool down to room temperature.
Measure the length of each of three places in the vertical direction, marked at the beginning, to 0.1 mm.
The shrinkage rate is calculated by the following formula, and the average value is calculated for each of the vertical and horizontal sides, and rounded to the first decimal place according to JIS Z 8401.

(8) Crystallization Size, Crystallinity Using an X-ray diffractometer (D8 DISCOVER with GADDS Super Speed, manufactured by Bruker AXS), measurement was performed in the range of 2θ = 10-40 °. At this time, the profile in all directions of the sample was measured. According to the method of Hindeleh et al. (AM Hideleh and D. J. Johnson, Polymer, 19, 27 (1978)), peak separation is performed based on the omnidirectional diffraction curve of commercially available metaaramid, and the highest intensity after separation is obtained. From the full width at half maximum of the peak (in the case of polymetaphenylene isophthalamide, around 2θ = 23.5 °), the crystal size (unit: Å) was calculated by the Scherrer equation shown below.
Crystal size = Kλ / (β × cos θ)
(Where K is a constant of 0.94, λ is the wavelength of the X-ray used, 1.54 mm (CuKα ray), β is the half-value width in radians of the reflection profile, the measured value is β _M , and the device constant is β _E was obtained from β = β _M −β _E. θ is the Bragg angle of the diffraction line.)
The crystallinity was determined from the ratio of the crystalline peak intensity after the separation to the total peak intensity. The crystallinity peak was based on the peak position of the diffraction intensity curve of a commercially available aramid fiber that was highly crystallized.

(9) Dust collection efficiency The collection efficiency was implemented based on the atmospheric dust counting method. A sample piece having a sample length of 20 cm and a sample width of 20 cm was prepared, and air at 200 ° C. containing dust having an average particle size of 0.5 μm at a concentration of 15 mg / m ³ at a wind speed of 6.0 m / min and an inner diameter. For each sample piece stretched so as to pass through a 110 mm cylinder and block the air flow in this cylinder, the dust concentration in the air before and after the sample piece is a forward scattered light receiving digital display using an optical laser diode as a light source. Measure with a dust meter. Then, the dust concentration before passing through the sample piece and the dust concentration after passing through the sample piece are measured, and the collection efficiency is obtained by the following formula. If the collection efficiency is 80% or more, ○, and the collection efficiency is less than 80% The thing was set as x.
Collection efficiency = [(Dust concentration before passage of sample piece−Dust concentration after passage of sample piece) / Dust concentration before passage of sample piece] × 100 (%)

(10) Pressure loss (KPa)
When measuring dust collection efficiency, measure the pressure before and after passing through the sample piece before and after the sample piece, and the pressure difference is the pressure loss. X.

[Example 1]
Polymetaphenylene isophthalamide powder (invented by Teijin Techno Products, 1.38 g / cm ³ ) having an intrinsic viscosity (IV) of 1.35 produced by an interfacial polymerization method according to the method described in Japanese Patent Publication No. 47-10863 A part was put into 80 parts by weight of dimethylacetamide (DMAc) cooled to 0 ° C. to make a slurry, and then heated to 45 ° C. and dissolved to obtain a polymer solution.
The above polymer solution was fed at 120 g / min to a spinning apparatus of US Pat. No. 6,013,223 using a gear pump, the spinning temperature was 35 ° C., and compressed air was fed at 10 m ³ / min for spinning. Here, in the spinning device of US6031323, 500 polymer solution discharge nozzles are arranged in an array of 100 × 5 rows, and the discharge holes having a hole diameter of 0.2 mm are arranged at equal intervals with a pitch of 5 mm. Used. Using water as the coagulation liquid, spraying the polymer solution at a position 40 cm downward from the nozzle hole with a spray nozzle at a water volume of 9 L / min to solidify the polymer solution to obtain a continuous fiber It was. Further, a collection belt was installed 50 cm below the spinning device, and continuous fibers were laminated thereon to obtain a fiber configuration and fabric weight as shown in Table 1.
The obtained non-woven fabric was heat-treated with a metal calender roll at a temperature of 250 ° C. and a set linear pressure of 50 kg / cm, and a linear pressure was arbitrarily adjusted by providing a clearance between the upper and lower rolls. The nonwoven fabric used as a material was obtained. The evaluation results are summarized in Table 1. The continuous fiber had a crystallinity of 51.8% and a crystal size of 19.7 mm.

[Examples 2 to 5, Comparative Examples 1 to 4]
In Example 1, the amount of compressed air, the collection belt speed, and the calendering conditions were changed so that the structure, basis weight, thickness, apparent density, and pore diameter of the fiber became a nonwoven fabric that becomes a filter material shown in Table 1, and the nonwoven fabric was changed. Was made. The evaluation results are summarized in Table 1.

[Example 6]
In Example 1, the obtained non-woven fabric was laminated with a fiber structure (made by Teijin Techno Products, weight per unit: 450 g / m ² , thickness 1.7 mm) which is a felt composed of polymetaphenylene isophthalamide fiber, and obtained. The obtained laminate was calendered at a temperature of 150 ° C., 50 kg / cm, a spacer of 1 cm, and a roll speed of 1 m / min to obtain a filter composite material comprising a nonwoven fabric layer and a fiber structure layer as a filter material. The evaluation results are summarized in Table 1.

[Comparative Example 5]
A polyester nonwoven fabric (manufactured by Toyobo Co., Ltd.) having a fiber configuration, basis weight, thickness, apparent density, and void diameter described in Table 1 was prepared, and performance was evaluated as a filter material. The evaluation results are summarized in Table 1.

[Comparative Example 6]
A polypropylene non-woven fabric (Tremicron, manufactured by Toray Industries Inc.) having a fiber configuration, basis weight, thickness, apparent density, and void diameter described in Table 1 was prepared, and performance was evaluated as a filter material. The evaluation results are summarized in Table 1.

[Comparative Example 7]
A nonwoven fabric used in Comparative Example 6 and a fiber structure (made by Teijin Techno Products, weight per unit: 450 g / m ² , thickness 1.7 mm) which is a felt made of polymetaphenylene isophthalamide fiber were laminated and obtained. The laminate was calendered at a temperature of 100 ° C., 50 kg / cm, a spacer of 1 cm, and a roll speed of 1 m / min to obtain a filter composite material comprising a nonwoven fabric layer and a fiber structure layer. The evaluation results are summarized in Table 1.

  As is clear from these results, the filter material and filter composite material satisfying the requirements of the present invention are excellent in heat resistance and flame retardancy, hardly shrink even under a high temperature atmosphere, and the pressure loss does not increase remarkably, It was confirmed that fine dust having a particle size of the order of submicron also showed excellent collection efficiency.

The filter material and filter composite material of the present invention have a function of collecting and removing contaminants in the air, such as dust, and purifying the air, and are discharged from a garbage incinerator, a coal boiler, or a metal blast furnace. The filter can be suitably used as a bag filter in which a filter cloth for collecting dust and a filter material or the like for filtering high-temperature exhaust gas is sewn. It also serves as a protective material for members that require heat resistance. Furthermore, when using a meta-aramid fiber as the fiber constituting the filter material and heat resistance, it also has chemical resistance, so it can be used under acidic and alkaline conditions. Target value is extremely high.

Claims (7)

A filter material comprising a nonwoven fabric composed of continuous fibers, wherein the continuous fibers satisfy (a) and (b), and the nonwoven fabric satisfies (c), (d), and (e) .
(A) The average fiber diameter of continuous fibers on the nonwoven fabric surface is 0.1 to 10 μm.
(B) The melting point or thermal decomposition temperature of the continuous fibers constituting the nonwoven fabric is 300 ° C. or higher. (C) The apparent density of the nonwoven fabric is 0.05 to 1.0 g / cm ^3.
(D) The average void diameter of the nonwoven fabric is 0.5 to 10 μm and the maximum void diameter is 20 μm or less. (E) The dry heat shrinkage rate of the nonwoven fabric at 200 ° C. is 2% or less. The filter material according to claim 1, wherein the continuous fibers constituting the nonwoven fabric are aramid fibers . The filter material according to claim 2 , wherein the continuous fibers constituting the nonwoven fabric are polymetaphenylene isophthalamide fibers. The filter material according to claim 2 , wherein the continuous fibers constituting the nonwoven fabric are polyparaphenylene terephthalamide fibers or copolyparaphenylene 3,4'-oxydiphenylene terephthalamide fibers. A filter comprising the filter material according to any one of claims 1 to 4 and a fiber structure made of any one of a woven fabric, a knitted fabric, and a nonwoven fabric made of aramid fibers, or a combination thereof. Composite material. Fibers polyparaphenylene terephthalamide fibers constituting the fiber structure, co polyparaphenylene 3,4'-diphenylene terephthalamide fibers, poly-m-phenylene isophthalamide either fibers or claim 5, wherein consisting of combinations Filter composite. Filter material according to any one of claims 1-4, or a bag filter, wherein the filter composite of claim 5 or 6 is sewn into a bag shape.